Photovoltaic (PV) devices, such as solar panels, are used to collect convert incident radiation from the sun (sunlight) into electricity. Such solar panels generate electricity directly from sunlight semiconductor materials in which electrons are freed by solar energy and can be induced to travel through an electrical circuit. In use, an array of one or more solar panels is typically installed on a roof, or on one or more carriers affixed to the ground or another substrate, to catch as much sunlight as possible.
Maximizing the amount of sunlight impinging on the solar panels maximizes the amount of energy collected and converted to electricity by solar panels. The amount of sunlight that can be collected by solar panels is limited by a number of factors. Generally, each solar panel has a planar sunlight-collecting surface. The total area of the sunlight-collecting surface of a single solar panel, or of the collective sunlight-collecting surfaces of two or more solar panels in an array, is one factor affecting the amount of sunlight which can be collected. Thus, multiple solar panels are often used together to enlarge the total sunlight-collecting surface area, because there are practical limits to how large each panel can be manufactured. When more than one solar panel is used, three solar panels may be positioned with their sunlight-collecting surfaces lying generally in the same plane, facing the same direction.
Another way to increase the amount of sunlight collected by the solar panels is to attach one or more reflector panels at the outer periphery of the sunlight-collecting surfaces of the solar panels to reflect and concentrate incident sunlight on to the sunlight-collecting surfaces. The sunlight thus reflected would otherwise fall outside the periphery of the sunlight-collecting surface area and be lost. Thus, use of one or more reflective panels in addition to the solar panels increases the efficiency of solar energy collection systems.
Maximizing the amount of direct sunlight impinging on the solar panels also maximizes the total amount of energy collected for conversion. “Direct” sunlight means sunlight that impinges on the panel surfaces at a right angle, or as close to a right angle as possible. Direct sunlight carries more energy than indirect sunlight. Thus, other ways of increasing the amount of direct sunlight collected involve properly positioning the solar panels relative to the position of the sun in the sky to maximize the direct sunlight impinging on the solar panels.
For example, the sun appears in the sky at different altitudes (i.e., vertical angle from the horizon or the horizontal plane), rather than always directly overhead, depending on one's latitudinal location on the earth. This means that positioning solar panels flat on the ground would be inefficient in most places on earth. When located in the northern hemisphere such as Europe, North America, Japan, and northern Asia, or in the southern hemisphere such as South Africa, Australia, and southern South America, solar panels are tilted at an appropriate altitude. The altitude is selected based on the location to maximize the amount of direct sunlight that impinges on the sunlight-collecting surfaces of the solar panels throughout the day. In locations closer to the equator such as northern Brazil, Columbia, sub-Saharan Africa. Indonesia, and Singapore, where the sun's daily path across the sky remains at or close to directly overhead, significant tilting is less important and solar panels are typically installed with their surfaces at or nearly parallel with the horizontal plane of the earth. Selecting the altitude at which to orient solar panel arrays addresses differences in the sun's altitude from place to place on earth.
Throughout each day, at any given location on earth, the sun's position will also vary from east to west as it crosses the sky between sunrise and sunset. The position of the sun as it moves across the sky is measured as an angle on the horizontal plane known as azimuth. More specifically, the azimuth of the sun may be defined as the angle, drawn on the horizontal plane, between a fixed reference vector (e.g., a vector pointing due north) and a vector projecting from a given location (e.g., location of the solar panels) and a point of interest (e.g., the sun). In other words, the azimuth of the sun is the horizontal angle measured clockwise from a fixed base direction line such as north.
Historically, solar panel arrays remained in the same position with respect to the azimuth position of the sun, all day and all year round. These “static” arrays are limited in the amount of energy that can be produced in a given day because the arrays are not oriented to directly face the sun as it travels across the sky from sunrise to sunset.
It is an object of the invention to increase the effective amount of area of sunlight impinging on a given array by reflecting sunlight onto the array from areas where sunlight impinges outside of the array. It is another object of the invention to increase the amount of energy produced by a solar array by providing a system that automatically rotates a panel or an array of panels to face the sun as the sun travels from sunrise to sunset, thus increasing the amount of solar energy collected in a solar day.